In a traditional incandescent lamp, a TRIAC dimmer is generally used for dimming. Since a purely resistive filament is used in the incandescent lamp, when a current flows through the purely resistive filament, the purely resistive filament is conducted to emit light, and there is always a current flowing through the TRIAC dimmer. Therefore, it is unnecessary to supply an additional current to the TRIAC dimmer. As incandescent lamps are gradually replaced by light emitting diode (LED) lamps, the TRIAC dimmer is still retained. Since the LED is a non-resistive direct-current driven device, an LED driving power supply is required to output a direct current, so as to supply power to the LED and maintain drive the LED with a constant current. The existing LED driving power supply is usually classified into a switching power supply and a linear power supply. The switching power supply includes an energy storage element, and thus can directly supply a holding current to the TRIAC dimmer, but the switching power supply is expensive. The linear power supply is gradually used to drive the LED by virtue of low price and a simple circuit thereof. However, only in a case where an input voltage is greater than an output voltage in the linear power supply, a current may flow through an LED load, so as to turn on the TRIAC dimmer. In a case where the input voltage is lower than the output voltage, no current flows through the LED load, so as to turn off the TRIAC dimmer, resulting in flashing of the LED lamp during dimming. Therefore, a current holding circuit for the TRIAC dimmer is required in the linear power supply.
A non-flicker LED filament lamp in the conventional technology includes a linear constant-current driving power supply and an LED illuminator. The driving power supply includes an overcurrent protecting unit, a rectifying and filtering unit, a linear constant-current unit, a constant-current filtering unit and a flicker eliminating unit. The flicker eliminating unit is used for converting an output current of the constant-current filtering unit into a direct current having no current ripple. An input terminal of the overcurrent protecting unit is connected to commercial alternating-current power, an output terminal of the overcurrent protecting unit is connected to an input terminal of the rectifying and filtering unit, an output terminal of the rectifying and filtering unit is connected to an input terminal of the linear constant-current unit, an output terminal of the linear constant-current unit is connected to an input terminal of the constant-current filtering unit, an output terminal of the constant-current filtering unit is connected to an input terminal of the flicker eliminating unit, and an output terminal of the flicker eliminating unit is connected to the LED illuminator. The non-flicker LED filament lamp further includes a dimmer. A dimmer holding current supplying unit connected to the dimmer is connected between the output terminal of the rectifying and filtering unit and the input terminal of the linear constant-current unit. The driving power supply of the non-flicker LED filament lamp is a linear power supply. The driving power supply includes the dimmer holding current supplying unit, which may supply two parts of current to the dimmer. The dimmer holding current supplying unit has a complicated circuit, a great number of elements, high price and large circuit loss, resulting in low efficiency of the driving power supply.